The present invention relates to a wire electrical discharge apparatus, and more particularly to a wire electrical discharge apparatus which permits stable supply of electricity to a wire electrode and improves the service life of electrical supply members by suppressing abnormal wear due to vibrations accompanying the traveling of the wire electrode.
In general, a wire electrode (hereafter referred to as the wire), after processing a workpiece, is further fed continuously in a downstream direction. As for the passed wire after processing, discharge craters are formed on the wire surface due to the effect of discharge energy supplied for processing, so that the wire surface is roughened and is microscopically an irregular surface. For this reason, on the contact surface of a lower electrical supply member, e.g., a lower electrical supply die, which is disposed downstream, the wire travels while the roughened surface is brought into contact with the lower electrical supply die. Further, vibrations of the wire accompanying the travel are added, and states of contact and half contact are produced, so that very small arc discharges occur locally between the surfaces of the wire and the lower electrical supply member. Consequently, the surface of the lower electrical supply die is roughened, and the wire which is softer than the material of the lower electrical supply die is mechanically cut, and wire dust is produced.
The supply of electricity to the wire of the wire electrical discharge apparatus is an extremely important element in continuing the processing, and although various attempts have been made to improve stable electrical supply to the narrow wire, the present situation is such that sufficient achievements have not yet been obtained. As a conventional electrical supply member, as disclosed in Japanese Patent Examined Publication No. 14374/1987 or Japanese Patent Unexamined Publication No. 2417/1992, an electrical supply member is known in which a hollow cylindrical die having a small diameter allowing the wire to pass therethrough is fitted and fixed to an upper wire guide and a lower wire guide which are respectively arranged above and below a workpiece or are arranged to clamp the workpiece, and contact supplying of electricity is effected at a small-diameter inner surface provided in the center of the hollow cylindrical electrical supply die. However, this conventional electrical supply member has a diameter several times larger than that of the wire to allow a working fluid to pass through the small-diameter portion to cool the discharge heat accompanying the contact. For this reason, discharge takes place between the contact surfaces of the wire and the electrical supply die as processing advances, with the result that the electrical supply die becomes worn, and the positions of electrical supply surfaces that can be used have been limited to several locations. Furthermore, in this case, it is necessary to cut the small-diameter hole in the electrical supply die, so that hole cutting has therefore been difficult, and there has been a drawback in that the cost of the electrical supply die becomes high.
According to this conventional technique, however, since the electrical supply surfaces for the wire are small-diameter inner surfaces and are concave, the electrical supply surfaces have the effect of suppressing the vibration of the wire, with the result that the electrical supply die sufficiently comes into contact with the wire which has passed after processing the workpiece. Hence, although the service life of the electrical supply die is short, stable processing is possible.
In addition, as the second prior art, to make improvements over the drawbacks of the above-described first prior art, as disclosed in, for example, Japanese Utility Model Examined Publication No. 3026199, there is an electrical supply member in which the electrical supply die formed in a cylindrical or prismatic shape instead of the hollow cylindrical shape, and electrical supply surfaces are formed on its outer surface. As compared with the above-described electrical supply member having the hollow cylindrical shape, external contact is established, so that the outer shape of the electrical supply die can be set to be large, and positions for causing contact supplying of electricity can be provided in a greater number. For this reason, the number of times in the replacement frequency due to the wear of the electrical supply die decreases, making it possible to hold down the maintenance cost. However, since the electrical supply member of this second conventional art employs cylindrical external electrical supply, there is a drawback in that the contact surface becomes a convex surface, so that the traveling wire does not stabilize. Hence, trouble has been encountered in which because of an increase in the discharge phenomenon due to the runout of the wire during traveling, the contact surface of the electrical supply die becomes roughened and cuts the wire, resulting in such as the occurrence of wire dust.
To control this situation, there arise such inconveniences as the need to restrain the wire traveling speed and to hold down electric energy supplied to the wire, so that there have been cases where difficulties are caused to processing. Further, the aforementioned wire dust causes clogging in the wire guide located on the downstream side in the wire feeding direction between the wire guides which are set at positions for clamping the electrical supply die therebetween.
The present invention has been devised to eliminate the above-described drawbacks of the conventional art, and it is a primary object of the present invention to enlarge the outer shape of the electrical supply member and to prevent the production of erosion dust of the wire caused by the roughened surface of the electrical supply member by presenting the lateral runout of the traveling wire, which has passed after processing, due to its vibration or the like, thereby preventing unstable processing or preventing the clogging occurring in the downstream wire guide.
Further, a second object is to make the upper electrical supply member and the lower electrical supply member identical in shape, thereby preventing an increase in the kinds of component parts and lowering the maintenance cost.
Further, a third object is to permit accurate indexing to enable the use of the electrical supply members a plurality of times and to prevent a faulty indexing position.
Further, a fourth object is to prolong the life of the electrical supply members in conjunction with the extension of processing time due to automated operation and the like by adopting a material of higher hardness so as to improve the service life of the electrical supply member.
Further, since the need to attach or detach the electrical supply member easily has been required in the light of operating efficiency, a fifth object is to allow the electrical supply to be easily attached or detached by using a jig or the like and to facilitate the indexing of the electrical supply member.
Further, a sixth object is to enable use of the electrical supply number at a greater number of indexed positions so as to make effective use of the electrical supply members.
In accordance with the present invention, there is provided a wire electrical discharge apparatus for processing a workpiece by generating a discharge with a working fluid disposed between a wire electrode and the workpiece, said wire electrical discharge apparatus including a first guide and a second guide which are disposed in face-to-face relationship with the workpiece placed therebetween and respectively have electrical supply members for supplying electricity to the wire electrode, characterized in that said first guide is disposed on an upstream side in a wire feeding direction with respect to said second guide, a plurality of groove portions are formed in a surface of said electrical supply member provided in said second guide in such a manner as to extend in a traveling direction of the wire electrode, and said groove portions form electrical supply portions with respect to the wire electrode.
In addition, in the wire electrical discharge apparatus of the present invention said electrical supply member provided said first guide is structured in the same shape as that of said electrical supply member provided said second guide.
In addition, in the wire electrical discharge apparatus of the present invention, a plurality of groove portions are formed in a surface of said electrical supply member provided in said first guide in such a manner as to extend in the traveling direction of the wire electrode, electrical supply portions of said electrical supply member with respect to the wire electrode are each formed by a projecting portion between adjacent ones of groove portions formed in a surface of said electrical supply member, each of said electrical supply portions of said electrical supply member provided in said second guide with respect to the wire electrode is formed by each of said groove portions, and retaining portions in a number identical to that of the number of said groove portions formed in the surface of each of said electrical supply members are formed on each of said electrical supply members for controlling rotation of said electrical supply member.
In addition, in the wire electrical discharge apparatus of the present invention, the material of each of said electrical supply members is formed of a powder sintered metal or a material having properties similar thereto, and the surface of each of said electrical supply members is coated with a carbide or a nitride.
In addition, in the wire electrical discharge apparatus of the present invention, attachment and detachment of each of said electrical supply members are effected by using a drawing-out member which engages said electrical supply member, and said drawing-out member is provided with a rotation stopping member formed of a resilient member and permitting indexing of an electricity-supplying position of said electrical supply member.
In addition, in the wire electrical discharge apparatus of the present invention, a rotation stopping member disposed at an electrical supply portion formed in said electrical supply member provided in said first guide with respect to the wire electrode and a rotation stopping member disposed at an electrical supply portion formed in said electrical supply member provided in said second guide with respect to the wire electrode are arranged at angles which are different by an angle formed by said groove portion formed in said guide and an adjacent groove portion with respect to a central portion of said electrical supply member.